1. Field of the Invention
The present invention relates to a recording medium scanning system for scanning a recording medium with a light beam such as a laser beam modulated by a recording signal to record desired information on the recording medium, and more particularly to such a recording medium scanning device having a scanning speed correcting means for preventing noise produced by variations in the scanning speed of the light beam from being recorded on the recording medium.
2. Description of the Prior Art
One conventional recording medium scanning system includes a light source for generating a scanning light beam, a light modulator for modulating the scanning light beam with a recording signal, and a scanning means for scanning a recording medium with the modulated light beam, or recording light beam, issued from the light modulator.
In the known recording medium scanning system, the recording light beam from the light modulator is deflected by the scanning means, such as a galvanometer mirror, to scan the recording medium which may comprise a film or a photosensitive sheet of paper. At times, the scanning speed at which the recording light beam traverses the recording medium tends to vary due to, for example, a variation in the speed of movement of the scanning means, such as a variation in the swinging movement of the galvanometer mirror. If the scanning speed varies, then the information recorded on the recording medium will contain noise arising from the scanning speed variation. Therefore, such scanning speed variations prevent the desired information from being recorded with high accuracy.
One general solution to the aforesaid problem would be to control the speed of movement of the scanning means for removing undesirable variations from the speed of movement thereof. This speed control process can remove low-frequency speed variations from the speed of movement of the scanning means. However, it is incapable of removing high-frequency speed variations since the scanning means cannot be controlled to follow such high-frequency speed variations.